Silage compression or compacting apparatus, like for example the general system shown in U.S. Pat. No. 4,046,068, sometimes employs a hydraulic circuit including hydraulic pumps and motors for driving the various parts of the system including the means for compressing the silage. As rather large forces are involved and required to drive the various parts of the apparatus to effect the cutting and compaction of the silage, a substantial amount of heat is generated and the hydraulic fluid becomes heated to relatively high temperatures. Cooling must be provided for the hydraulic fluid and this has normally taken the form of coolant radiators of substantial extent. Inasmuch as the silage compacting apparatus of the type herein involved is used primarily in the field and moves at a very slow rate, large coolant radiators are required in order to maintain the hydraulic fluid at workable temperatures.